Sydney: Teaching over-protective parents to control their emotions could be the key to preventing mental illness in their children, researchers have claimed.

A team from Macquarie University has found treating parents of very shy girls as young as the age of three could help prevent them from developing depression and anxiety in their teenage years, reported a newspaper.Director of the centre for emotional health at Macquarie, Ron Rapee, said major risks for severe shyness developing into anxiety or depression in later life appeared to be over-protection and over-involvement of parents, as well as harsh and critical parenting.

"These are the sort of kids who don't say 'boo' ... they hang around their mother's legs and don't say hi to anyone," he said. His study followed more than 100 very shy children, teaching the parents of half to encourage them and to deal with their own emotional issues.

"We were teaching parents different strategies to try to build confidence in their children," he said.

The girls, who were about three-years-old when the study started, were 15 percent less likely to develop an anxiety disorder by their teenage years if their parents were given the treatment. Almost none developed depression, compared to about 16 percent of the untreated girls, Professor Rapee told an Australian Science Media Centre briefing. But the treatment did not show any effect in boys, he said.

Jane Fisher, a professor of women's health and director of the Jean Hailes research unit at Monash University, said girls and women who were not given the same opportunities as boys were more at risk of mental illness.

"I think it's possible that if parents are enabled early on in a little girl's life not to be excessively protective but to encourage her to experience mastery, to take risks - the things that are normative in care of boys - there is a very high likelihood that her psychological development is protected and enhanced," she said.